Replacing a steam main vent

tkos115

I would like to replace my steam main vent with a big mouth main vent. Currently I have a Vent Rite No. 35 which seems too small for my system. Overall my steam vent main pipe is approximately 57ft. long and 3in diameter. My port is 3/4in thread for the vent. I only have about 6in from the main threaded port until it would hit my subfloor underneath. Would 1 bigmouth vent work for this, or would I need more than 1? Also would this still fit with the clearance I have? The threaded part does sit up a few inches from the main. Is there a part number anyone would recommend for a big mouth vent?


Thanks for your help!

Jamie Hall

That poor little Ventrite hasn't a chance. Yes, you should be able to get a Big Mouth in there, on a shorter nipple. However, though I like the Big Mouth as well as anyone else, on that short a nipple I'd prefer to use a Gorton #2, as they have a float and are less subject to spitting if you have wet steam or condensate in the main.

Unhappily, they are about 6 1/2 inches high. Perhaps more to the point you may not have enough clearance to screw it on from that joist right next to it. The Big Mouth is shorter (4 3/4) and might, for that reason, be the better choice.

tkos115

Yeah it would be a very tight fit for the Gorton unfortunately. Would the nipple that's on their now need to be shortened for the bigmouth to work correctly or would it be fine on that?

Jamie Hall

I'd go with a shorter nipple.

Fred

From the looks of your picture, there isn't enough room to turn a one piece main vent on (other than something like what is there which is next to no venting at all).
The Bigmouth (part #BJ-3BM) has a total length of 4.75", when screwed in it is about 4.25". It is a two piece design so you can screw the tail piece (union) into your existing pipe and then place your vent on the union and tighten the union nut. The wide part of the vent does not need to turn against that joist. just face the vent port out opposite the floor joist. One vent should be enough. You need a 5/8" hex wrench to install and tighten the tail piece into your pipe.
I see Amazon is currently out of stock. I see Supplyhouse.com has them in stock:
https://www.supplyhouse.com/sh/control/search/~SEARCH_STRING=barnes & jones air vents?searchText=barnes+&+jones+air+vents

tkos115

I ended up getting a big mouth from the supply house site. Works way better and vents much faster. I noticed that my kitchen radiator seems to be on it's own main line. Basically, as the main comes out of the boiler it goes over to the edge if my foundation and splits at a T. When it goes to the right it serves as the main for all my radiators minus my big kitchen one. When it goes to the left, it goes about 4 feet then goes to my kitchen radiator which also happens to be the biggest one in the house. The main that goes to the kitchen radiator doesn't have a main vent on it. It heats relatively decent but seems a bit slow still. Would a large radiator vent be acceptable rather than adding a spot for a main vent?

The circled red section is the main that goes to the kitchen radiator.

dopey27177

Venting steam systems is not as simple as picking a big main vent valve. Vent valve manufacturers size vent valves and indicate the capacity to vent air out of pipes and radiators.

Example: as shown in the book STEAM the perfect fluid for heating and some of the problems available at Barnes and Noble and Amazon and Dorrance publishing Pittsburgh Penn.
Hoffman #1 series vent valve used on radiators, pressure operation 1-10 psig, air removal capacity 150-800 cubic feet per minute. A Gorton #1 air eliminator used as an end of the line main vent valve has a venting capacity of 4.08 cubic feet of air at 1 psig.

Look at the disparity between two vent valves. Why is this,
the Hoffman #1 vent valve only needs to vent the air from one radiator. The Gorton #1 vent valve needs to vent the air from the boiler and the steam main.

How do we decide what vent valves to use?
first we need to know how many cubic feet of steam is produced by the boiler and how many cubic feet of air space is in the piping and radiators.

After is calculated you may find that the Hoffman @1 vent valve will vent all the air out of the system in one hour. Steam boiler ratings are based on ponds of steam per hour,

in reality we need to deliver steam to the radiators in about 20 minutes so we need to add a quick vent on the end of steam mains.

Here the velocity of steam in the system comes into play. If the speed of the steam is hampered by the size of the pipe the high capacity vent valve will not operate at high capacity. If the speed of the steam is correct the high capacity vent valve will operate at maximum efficiency.

Picking the right high capacity vent valve goes something like this, all the radiator vent valves cumulatively will vent all the air out the system in one hour. To give the system a kick we select a main vent valve.

Using rough figures 100,000 btu boiler will produce 100 lbs of steam per hour and that translates 2500 cubic feet of steam per hour, which is divide by 60 and we have an air capacity of 40 cubic feet per minute.

The Gorton # 1 vent eliminates 4 cubic feet per minute so in 10 minutes the air can be vented from the boiler and steam main.

Do we need a Gorton vent valve on the steam main maybe not. Remember the radiator vent valve discharge air as well. We then use a Gorton # C, which vents about half the air.

This writing is to make you aware vent valve sizing is not guess work, it takes some thought and understanding what goes on in a steam heating system.

Operating steam pressure and drop back pressure affects how a vent valve works. Not the knowledge you learned because it worked somewhere else or what the countermen told you.

Jacob Myron

Buy the book and learn a lot more about vent valves and steam heating systems.

ChrisJ

dopey27177 said:

Venting steam systems is not as simple as picking a big main vent valve. Vent valve manufacturers size vent valves and indicate the capacity to vent air out of pipes and radiators.

Example: as shown in the book STEAM the perfect fluid for heating and some of the problems available at Barnes and Noble and Amazon and Dorrance publishing Pittsburgh Penn.
Hoffman #1 series vent valve used on radiators, pressure operation 1-10 psig, air removal capacity 150-800 cubic feet per minute. A Gorton #1 air eliminator used as an end of the line main vent valve has a venting capacity of 4.08 cubic feet of air at 1 psig.

Look at the disparity between two vent valves. Why is this,
the Hoffman #1 vent valve only needs to vent the air from one radiator. The Gorton #1 vent valve needs to vent the air from the boiler and the steam main.

How do we decide what vent valves to use?
first we need to know how many cubic feet of steam is produced by the boiler and how many cubic feet of air space is in the piping and radiators.

After is calculated you may find that the Hoffman @1 vent valve will vent all the air out of the system in one hour. Steam boiler ratings are based on ponds of steam per hour,

in reality we need to deliver steam to the radiators in about 20 minutes so we need to add a quick vent on the end of steam mains.

Here the velocity of steam in the system comes into play. If the speed of the steam is hampered by the size of the pipe the high capacity vent valve will not operate at high capacity. If the speed of the steam is correct the high capacity vent valve will operate at maximum efficiency.

Picking the right high capacity vent valve goes something like this, all the radiator vent valves cumulatively will vent all the air out the system in one hour. To give the system a kick we select a main vent valve.

Using rough figures 100,000 btu boiler will produce 100 lbs of steam per hour and that translates 2500 cubic feet of steam per hour, which is divide by 60 and we have an air capacity of 40 cubic feet per minute.

The Gorton # 1 vent eliminates 4 cubic feet per minute so in 10 minutes the air can be vented from the boiler and steam main.

Do we need a Gorton vent valve on the steam main maybe not. Remember the radiator vent valve discharge air as well. We then use a Gorton # C, which vents about half the air.

This writing is to make you aware vent valve sizing is not guess work, it takes some thought and understanding what goes on in a steam heating system.

Operating steam pressure and drop back pressure affects how a vent valve works. Not the knowledge you learned because it worked somewhere else or what the countermen told you.

Jacob Myron

Buy the book and learn a lot more about vent valves and steam heating systems.

I originally tried all of this and none of it worked.
Even after multiple attempts.

You can't overvent a main. Unless you have a main that heats faster than another main, then you can slow it down if need be to get them matched.

I have 5 Gorton 1's on a 33' 2" main and a single Gorton 1 on a 11' 2" main. I judge my main venting by heating the system, turning it off for 5 minutes and starting it again and watching the pressure at the boiler. If I build any amount of backpressure when the mains are hot I consider that to be an issue.

ChrisJ

tkos115 said:

I ended up getting a big mouth from the supply house site. Works way better and vents much faster. I noticed that my kitchen radiator seems to be on it's own main line. Basically, as the main comes out of the boiler it goes over to the edge if my foundation and splits at a T. When it goes to the right it serves as the main for all my radiators minus my big kitchen one. When it goes to the left, it goes about 4 feet then goes to my kitchen radiator which also happens to be the biggest one in the house. The main that goes to the kitchen radiator doesn't have a main vent on it. It heats relatively decent but seems a bit slow still. Would a large radiator vent be acceptable rather than adding a spot for a main vent?



The circled red section is the main that goes to the kitchen radiator.

You can mess around with it.
If you vent the radiator really fast it may work fine, or it may spit or overheat the room. The only way to know for sure is to try.

No reason not to give it a whirl in my opinion.
If it doesn't work out, you could also drill and tap the pipe side of the radiator and add another faster vent to that side of it. A Gorton C or D and then use a slower vent on the other side to vent the radiator at a more reasonable speed.

dopey27177

The Gorton C or D are to large for a radiator. try the Gorton #6t will vent 1.6 cubic feet of per minute at 1 psig thats about 4 times faster than the average radiator vent valve,

Another item to check is the boilers operating pressure,

normally 2 psig operating pressure with a 1/2 pound dropin pressure is perfect in a building. your pressure controller should allow that adjustment. not knowing your system you may have to up the steam pressure a little.

Jacob Myron

ChrisJ

dopey27177 said:

The Gorton C or D are to large for a radiator. try the Gorton #6t will vent 1.6 cubic feet of per minute at 1 psig thats about 4 times faster than the average radiator vent valve,

Another item to check is the boilers operating pressure,

normally 2 psig operating pressure with a 1/2 pound dropin pressure is perfect in a building. your pressure controller should allow that adjustment. not knowing your system you may have to up the steam pressure a little.

Jacob Myron

Hi Jacob,

In my opinion on a small residential system if you're at 1 PSIG and you're still venting radiation you're venting way too slow.

tkos115

My pressuretrol is currently set at .5 cut in and 1.5 cut out if im reading that correctly. Would bumping it up a bit be better for it? And I was thinking about trying a Gorton #6 but im gonna run some numbers first and try to figure out the best one based on length and volume.

ChrisJ

tkos115 said:

My pressuretrol is currently set at .5 cut in and 1.5 cut out if im reading that correctly. Would bumping it up a bit be better for it? And I was thinking about trying a Gorton #6 but im gonna run some numbers first and try to figure out the best one based on length and volume.

If it works at those pressures reliably do NOT increase it.
Also, chances are if you didn't set it using an actual gauge, it's likely not running that low.

My system rarely goes above 0.0360912 PSIG and it heats the entire house.

ethicalpaul

It's that 7th significant digit that gets you!

ChrisJ

ethicalpaul said:

It's that 7th significant digit that gets you!

I just quickly converted 1" WC to PSIG and copied and pasted it.

Fred

@tkos115 , On a residential system, there is no advantage to setting the pressure up to 2psi.

dopey27177

Pressure settings in small homes can vary anywhere from 1 psig to 5 psig. this depends on the type of system. when it was installed and the size of the piping.

example: 100,000 btuh translate to 100 lbs of steam per hour.
100 lbs of steam per hour converts into 2500 cubic feet of steam per hour at 1 psig. Raise the steam pressure to 2 psig and the volume drops to 2400 cubic feet of space. At 10 psig the volume drops to 1600 cubic feet of space.

As you can see the higher the pressure the less steam you have available for heating.

I am not doing the math this comes off steam tables that are used by engineers.

In a properly designed steam systems the velocity of steam (speed through the piping) ranges from 10 feet per second to a max of 35 feet per second. The velocities are governed by the size of the piping.

Many two pipe steam heating systems installed between 1915 and 1930 on the north shore of long island (estate homes) had steam mains as large as 8" . These homes had steam radiators with no vent valves or steam traps.

The radiators were equip with radiator valves that had a fixed discharge setting or had orifices to provide a measured amount of steam to each radiator. The radiators only received the amount of steam required to heat the room.

Air was pushed out of the piping by the incoming steam and left the system by a master air release valve. The air was discharged from the building by piping attached to the outlet of venting device and piped to a chimney or piped through the wall to the outside of the building.

I do not deal in opinions. I deal in facts. One can experiment with the steam pressure settings and find the right one for a specific building, use that as a thumb rule and for then most part apply that to all buildings until you get to a building where the system was altered for expansion or asbestos insulation removed and the steam piping was not re-insulated.

I can go on and on about what can go wrong in any steam heating system in any building. Remember steam heating systems have been around since the 1700 or so. They range from engineered and properly designed to 1940s when many contractors installed steam systems in small homes and new apartment houses using thumb rules.

Jacob Myron

Fred

@dopey27177 , unfortunately some of what you are saying is, in fact opinion, not fact. Steam moves through mains faster at lower pressures than it will at higher pressures. Most, if not all radiator vents are rated at a max of 3psi and many, many of the two pipe systems, especially the vapor systems will not function properly, if at all, above a very few ounces (8 to 12 ounces max). I doubt that you will find any informed poster here or Pro who would suggest running a residential steam system above 2psi. Most will tell you around 1 to 1.5 psi max. I have a fairly large one pipe system, as residential systems go, and I run, with a vaporstat, at about 4 to 6 ounces, max. We are not discussing velocities, we are talking pressure. I might add, the larger the diameter of the pipe, the lower the steam velocity. That is why proper near boiler pipe sizing is so important. It slows the velocity down enough to allow the water droplets to fall out so that the steam is as dry as possible.

acwagner

@tkos115 I think running the numbers gets you the general venting strategy, but it will take some trial and error to get it to actually perform the way you want it.

I personally have every size Gorton radiator vent on my system--4, 5, 6, C, and D. The 4 is on a small radiator with around 2 feet of runout. The D is on a medium sized radiator on the second floor with something like 25-30 feet of runout/riser piping. That's what it took to get mine to be reasonably balanced and comfortable.

Shalom

@acwagner I'm still wondering why they numbered them that way, We know where 1 and 2 are (the main vents), but whatever happened to 3? or A and B?